Organometallic polymers and use thereof

ABSTRACT

Compositions comprising a polymer of organometallic polymerizable monomer acid or ester are useful as resists and are sensitive to imaging irradiation while exhibiting enhanced resistance to reactive ion etching.

CROSS REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. patent application Ser. No.09/350,937 filed Jul. 12, 1999 now U.S. Pat. No. 6,171,757.

DESCRIPTION Technical Field

The present invention relates to certain organometallic polymers whichare useful as photoresists and which exhibit enhanced resistance toplasma and especially to Cl₂/O₂ plasma used in reactive ion etching. Thepresent invention is concerned with the compositions-as well as theiruse in lithography. For instance, the materials of the present inventionare suitable for use in device and mask fabrication on optical, e-beam,x-ray and ion-beam lithography tools.

BACKGROUND OF INVENTION

In the manufacture of patterned devices and especially microelectronicdevices, the processes of etching different layers which constitute thefinished product are among the most crucial steps involved. One methodwidely employed in the etching process is to overlay the surface to beetched with a suitable mask.

The mask is typically created by imagewise forming a pattern of resistmaterial over those areas of the substrate to be shielded from theetching. The resist is normally formed of a polymeric organic material.The pattern is formed by imagewise exposing the resist material toirradiation by lithographic techniques. The irradiation employed isusually x-ray, UV radiation, electron beam radiation or ion-beamradiation.

Radiation sensitive materials and/or compositions are eitherpositive-acting (i.e. radiation solubilizable) or negative-acting (i.e.radiation insolubilizable or radiation crosslinkable). Positive-working(radiation) sensitive compositions are rendered soluble (or developable)by actinic radiation (deep-near UV, x-ray, electron-beam or ion-beam)and can be removed using selective developing solutions leavingunexposed areas intact. Negative-working (radiation) sensitivecompositions are those which become insoluble upon exposure to actinicradiation. Selected solutions can dissolve and remove the unexposedareas of the composition while leaving the exposed portions intact.Development of such exposed materials yields negative tone images.

After the resist is developed forming the desired mask, the substrateand mask can be immersed in a chemical solution which attacks thesubstrate to be etched while leaving the mask intact. These wet chemicalprocesses suffer from the difficulty of achieving well-defined edges onthe etched surfaces. This is due to the chemicals undercutting the maskand the formation of an isotropic image. In other words, conventionalchemical wet processes do not provide the resolution considerednecessary to achieve optimum dimensions consistent with currentprocessing requirements.

Moreover, such wet etching processes are undesirable because of theenvironmental and safety concerns associated therewith.

Accordingly, various so-called “dry processes” have been suggested toimprove the process from an environmental viewpoint, as well as toreduce the relative cost of the etching. Furthermore, these “dryprocesses” have the potential advantage of greater process control andhigher aspect ratio images. Also, when fabricating patterns havingfeature sizes below 350 nm, dry etching processes are necessary forprofile control.

Such “dry processes” generally involve passing a gas through a containerand creating a plasma in this gas. The species in this gas are then usedto etch a substrate placed in the chamber or container. Typical examplesof such “dry processes” are plasma etching, sputter etching, andreactive ion etching.

Reactive ion etching provides well-defined, vertically etched sidewalls.

One of the challenges in the fabrication of microelectronic devices andmasks is to develop a resist which exhibits good lithographicperformance as well as high dry etch resistance for subsequent patterntransfer into an underlying substrate. The dry etch chemistries includeO₂ currently used for antireflective coatings, Cl₂/O₂ currently used forchrome etching in mask fabrication, Cl₂ based plasma for polysiliconetch, and fluorocarbon based plasmas such as CF₄ for oxide etching.These plasmas are examples only and are not meant to limit the scope.Conventional novolak/diazonapthoquinone resists used for i-linelithography have to date exhibited the best dry etch resistance. ZEP isan e-beam resist which has been adopted by the industry for advancedmask making to replace the conventional wet etch polybutenesulfone (PBS)process. Although ZEP provides significant improvement over the PBSprocess, its dry etch resistance to Cl₂/O₂ is marginal (etch rate of1.95 nm/s). Novolac is 1.4 nm/s.

There is a need to develop radiation sensitive compositions that provideimproved dry etch resistance for use in mask fabrication (binary,attenuating phase shift masks, alternating phase shift masks) and fordevice fabrication.

Further, the use of polyvinyl diphenylferrocene and polyvinylferroceneas negative resists in ion implantation masking and in the formation ofconductive patterns has been suggested (see U.S. Pat. No. 3,885,076). Itis stated that the electron beam causes crosslinking of these polymersand renders negative patterns. Other polymers containing metal groupsare referred to in U.S. Pat. No. 4,156,745. Lead methacrylate, whenincorporated into copolymers with methylmethacrylate increases the speedof the resist compared to homopolymers of methylmethacrylate. The use ofpolyvinylferrocene has been proposed for oxidative decomposition to ironoxide patterns according to U.S. Pat. No. 4,027,052. The patterndelineation is accomplished by applying x-rays. Moreover, siliconcontaining resists have been quite prevalent. The use of silicon andgermanium has been intended to impart O₂ etch resistance to the resistmaterial. For example, see U.S. Pat. Nos. 4,764,247; 4,935,094 and5,733,706, and Microelectronic Engineering 3,279 (1985). Nevertheless,the prior art does not disclose any organometallic polymeric materialsfor masking against C₂ and Cl₂/O₂ RIE (reactive ion etching).

Cl₂ RIE and Cl₂/O₂ RIE are used in the electronics industry in etchingpolysilicon and in etching chromium in optical mask fabrication. Theetched patterns are differentiated from the unetched surface areas by alayer of resist material. The resist should have adequate resistancetowards the particular plasma used in the etching. Cl₂/O₂ plasma isregarded as one of the harshest environments to which a surface can besubjected. Examples of resists that are used for the above-mentionedapplications are e-beam resists such as ZEP 7000 and ZEP 520 used forpatterning chromium in the preparation of optical masks and copolymersof tert.-butyl methylacrylate, tert.-butyl methacrylic acid, andmethylmethacrylate, experimental resists, referred to herein as “X−1”,described in U.S. Pat. No. 5,071,730 and intended as a 193 nm UV resist.Other deep UV resists that are used for patterning in Cl₂/O₂ plasmainclude UV2 and UV6. ZEP resist has the chemical formula 1 shown below.

The etch rate of ZEP in Cl₂/O₂ plasma is 1.95 nm/sec compared to 1.40nm/sec for Novolac. This rate is regarded as marginal. The structure ofX−1 is shown below as formula 2. It also has a low resistance to Cl₂/O₂plasma because of the methacrylate backbone of the polymer.

Both ZEP and X−1 resists require an increase in their RIE resistanceproperties. Other commercial resists such as amplified resists (e.g.APEX E) for deep UV applications, could also benefit from a boost intheir RIE resistance properties.

SUMMARY OF INVENTION

The present invention provides compositions which are especially usefulas resists and which are sensitive to imaging irradiation whileexhibiting enhanced resistance to reactive ion etching. The compositionsof the present invention typically exhibit enhanced resistance toreactive ion etching using in particular Cl₂/O₂ plasma, Cl₂ plasmas, O₂plasmas and fluorocarbon plasmas.

In particular, the polymers of the present invention are from at leastone monomer selected from the group consisting of an organometallicacrylate, organometallic methacrylate, organometallic styrenes andmixtures thereof wherein the metal is selected from the group consistingof yttrium, aluminum, iron, titanium, zirconium, hafnium and mixturesthereof.

The present invention also relates to a method for forming a pattern ofa resist which comprises:

a) providing on a substrate a layer of a resist composition whichcomprises a resist from at least one monomer selected from the groupconsisting of an organometallic acrylate, organometallic methacrylate,organometallic styrenes and mixtures thereof wherein the metal isselected from the group consisting of yttrium, aluminum, iron, titanium,zirconium, hafnium and mixtures thereof.

b) imagewise exposing the layer of resist composition to irradiation;and

c) developing the resist to thereby form the pattern.

A further aspect of the present invention relates to forming a patternon a substrate which comprises:

a) providing a layer to be patterned on a substrate,

b) providing on the layer to be patterned a layer of a resistcomposition which comprises a photoresist from at least one monomerselected from the group consisting of an organometallic acrylate,organometallic methacrylate, organometallic styrenes and mixturesthereof wherein the metal is selected from the group consisting ofyttrium, aluminum, iron, titanium, zirconium, hafnium and mixturesthereof.

c) imagewise exposing the layer of resist composition to irradiation,

d) developing the resist to form the desired pattern, and

e) subjecting the layer to be patterned to reactive ion etching with theresist acting as a mask to thereby form the desired pattern on thesubstrate.

Still other objects and advantages of the present invention will becomereadily apparent by those skilled in the art from the following detaileddescription, wherein it is shown and described only the preferredembodiments of the invention, simply by way of illustration of the bestmode contemplated of carrying out the invention. As will be realized theinvention is capable of other and different embodiments, and its severaldetails are capable of modifications in various obvious respects,without departing from the invention. Accordingly, the description is tobe regarded as illustrative in nature and not as restrictive.

BEST AND VARIOUS MODES FOR CARRYING OUT INVENTION

The polymers employed according to the present invention are obtainedfrom polymerization of at least one organometallic monomer selected fromthe group consisting of an organometallic acrylate, organometallicmethacrylate, organometallic styrenes and mixtures thereof wherein themetal is selected from the group consisting of yttrium, aluminum, iron,titanium, zirconium, hafnium and mixtures thereof. The styrenes includesubstituted styrenes such as acetoxystyrene. Preferably at least atwo-carbon atom chain exists between the metallic moiety and acrylate ormethacrylate moiety.

The preferred metallic moiety is iron. Both homopolymers and copolymersare contemplated according to the present invention.

The polymers typically have average number molecular weights of about2000 to about 100,000, and preferably about 4500 to about 10,000.

Examples of such suitable organometallic monomers are 2-ferrocenylethylacrylate, 2-ferrocenylethyl methacrylate,2-(ferrocenylmethyl-2-urethano)-ethyl methacrylate,2(ferrocenylmethyl-2-urethano)-ethyl acrylate, 4-ferrocenylmethylstyrene, and 3 ferrocenylmethyl 4-acetoxy styrene.

In the case of copolymers, the other monomer is typically at least onemonomer selected from the group consisting of acrylic acid, methacrylicacid, esters thereof and mixtures thereof.

Examples of suitable monomeric esters are 2-hydroxyalkyl methacrylatesand 2-hydroxyalkyl acrylates wherein the alkyl has 1-10 carbon atoms;alkylacrylates and alkylmethacrylates thereof wherein the alkyl has 1-10carbon atoms; and chloroalkyl acrylates and chloroalkyl methacrylateswherein the alkyl has 1-10 carbon atoms.

The copolymers typically contain about 1% by weight to about 90% byweight, more typically about 10% by weight to about 70% by weight, andpreferably about 20% by weight to about 50% by weight, of theorganometallic monomer and correspondingly about 99%. to about 10% byweight, anbout 90% to about 30% by weight and about 80% by weight toabout 50% by weight of the other comonomer(s).

In addition, copolymers can further include other monomers such asstyrene, alphamethyl styrene, 4-hydroxy styrene, acetoxy styrene andother derivatives of hydroxystyrene.

Examples of some acrylates and methacrylates are:

2-hydroxyethyl methacrylate

2-hydroxypropyl methacrylate

2-hydroxyethyl acrylate

2-hydroxypropyl acrylate

2-hydroxybutyl acrylate

2-hydroxypentyl acrylate

methylmethacrylate

4-butylmethacrylate

methylacrylate

alphachloromethylacrylate

t-butyl methacrylate

t-butyl acrylate.

Examples of some copolymers according to the present invention are:

copolymers of alphachloromethyl acrylate and 2-ferrocenylethyl acrylate,

copolymers of alphachloromethyl acrylate and 2-ferrocenylethylmethacrylate,

copolymers of alphachloromethylacrylate, alphamethyl styrene and2-ferrocenylethyl acrylate,

copolymers of alphachloromethyl acrylate, alphamethyl styrene and2-ferrocenylethyl methacrylate,

copolymers of 2-ferrocenylethyl acrylate, methacrylic acid and t-butylmethacrylate,

copolymers of 2-ferrocenylethyl methacrylate, methacrylic acid andt-butylmethacrylate,

copolymers of alphachloromethyl acrylate and2-(ferrocenylmethyl-2-urethano-)-ethyl acrylate,

copolymers of alphachloromethyl acrylate and2-(ferrocenylmethyl-2-urethano-)-ethylmethacrylate,

copolymers of alphachloromethylacrylate, alphamethyl styrene and2-(ferrocenyl-methyl-2-urethano-)-ethyl acrylate,

copolymers of alphachloromethylacrylate, alphamethyl styrene and2-(ferrocenyl-methyl-2-urethano-)-ethyl methacrylate,

copolymers of 2-(ferrocenyl methyl-2-urethano-)-ethyl acrylate,methacrylic acid and t-butyl methacrylate,

copolymers of 2-(ferrocenylmethyl-2-urethano-)-ethyl methacrylate,methacrylic acid and t-butyl methacrylate,

copolymers of 2-ferrocenylethyl acrylate, α-methyl 4acetoxystyrene andt-butyl methacrylate,

copolymers of 2-ferrocenylethyl methacrylate, α-methyl 4-acetoxystyreneand t-butylmethacrylate,

copolymers of 2-(ferrocenyl methyl-2-urethano-)-ethyl acrylate, α-methyl4-acetoxystyrene and t-butyl methacrylate,

and copolymers of 2-(ferrocenylmethyl-2-urethano-)-ethyl methacrylate,α-methyl-4-acetoxystyrene and t-butyl methacrylate.

In the case of the above terpolymers, the amount of the organometallicmonomer is typically about 1 to 30% by weight and more typically about 1to about 20% by weight with the other comonomers correspondingly about70 to about 99% by weight and about 80% to about 99% by weight.

For example, terpolymers of alphachloromethyl acrylate, alphamethylstyrene and the organometallic monomer typically contain about 1-50% ofthe acrylate and about 1-80% of the organometallic monomer. Terpolymersof the organometallic monomer, methacrylic acid and t-butyl methacrylatetypically contain about 1 to about 25% of the organometallic monomer,about 5 to about 30% of the methacrylic and about 45 to about 90% of thet-butyl methacrylate.

An example of modification of X−1 by incorporating ferrocenyl groups isillustrated by formula 3 below.

In addition, the polymers of the present invention can be admixed withother resists to increase the RIE resistance of the other resists suchas ZEP and X−1. For instance, polymers of (1-ferrocenyl-2-oxyethane)methacrylate, including homopolymers thereof, can be blended with otherresists. When used in mixture, the amount of the polymers of the presentinvention are typically about 90 to about 1% by weight, more typicallyabout 70% by weight to about 10% by weight, and preferably about 50% byweight to about 20% by weight and, correspondingly, the other resist isabout 10 to about 99% by weight, about 30 to about 90% by weight andabout 50% by weight to about 80% by weight.

The polymers of the present invention are typically prepared by freeradical solution polymerization using a free radical catalyst such asAIBN and solvent such as tetrahydrofuran, isopropanol and toluene.

The polymerization is usually carried out at reflux temperature of thesolvent.

The polymers of the present invention can be developed employing anorganic solvent such as ethyl-3-ethoxypropionate.

The following illustrates a typical fabrication sequence for providingoptical masks for microlithography by providing a pattern of chromiummetal on a quartz plate by the following steps:

1. A thin film of chromium metal is provided on the surface of a quartzplate.

2. The metal layer is coated with e-beam resist.

3. The resist is patterned by e-beam.

4. The plate is developed in a suitable developer.

5. The exposed chromium film is etched either by wet etch or by dryetch.

6. The residual resist is removed.

The following non-limiting examples are presented to further illustratethe present invention.

EXAMPLE 1 Preparation of 2-Ferrocenylethyl Alcohol

2-ferrocenylethyl alcohol was synthesized by reducing ferrocenyl aceticacid with lithiumaluminum hydride. 1.4 g of LiAlH₄ are placed in a flaskcontaining ether and equipped with a soxhlet apparatus. Ferrocene aceticacid (0.9 g) is extracted by this apparatus for 48 hours. After cooling,the excess reagent is decomposed with water and the solution washedthoroughly with a solution of sodium bicarbonate, dried and evaporatedto dryness. The residual oil is crystallized from hexane. It has amelting point of 41° C.

EXAMPLE 2 Preparation of Ferrocenylethyl Methacrylate

2-ferrocenylethyl alcohol obtained from Example 1 (0.8 g) is dissolvedin 300 ml anhydrous ether and 0.4 g of pyridine are added. The solutionof 0.5 ml methacryloyl chloride in 30 ml ether is added dropwise and thereaction is continued for four hours. The precipitate is removed byfiltration and the ether solutions are combined, washed with 5% sodiumbicarbonate, 5% hydrochloric acid, sodium bicarbonate again and dried.The ether is evaporated, leaving a brown viscous oil that is furtherpurified by chromatography over silica (ether as eluent).

EXAMPLE 3 Preparation of Copolymer

Ferrocenylethyl methacrylate obtained from Example 2 was copolymerizedwith alphachloromethyl acrylate and alphamethyl styrene. For a1/4:1/2:1/4 mole ratio, a mixture of 0.785 g:0.5 g:0.295 g respectivelywas prepared. The mixture was placed in a glass tube together with 0.06g AIBN. The glass tube was evacuated and selated, then maintained at 75°C. for 24 hours. The polymer was freed from its monomers by dissolvingin THF followed by precipitation with hexane. It was found by GPC thatthe molecular weight of the polymer was about 1300.

EXAMPLE 4 Preparation of Composition Containing Copolymer

0.1 g of the copolymer obtained in Example 3 was mixed with 10 g ZEP7000A forming a homogenous solution. A film was spin coated onto siliconwafers. The film was continuous and did not display any componentsegregation. The film was tested for RIE etch rate. The etch rate wasfound to be 1.75 nm/sec compared with 1.95 nm/sec for ZEP.

EXAMPLE 5 Preparation of 2-(Ferrocenylmethyl-2-urethano)-ethylMethacrylate

5 g of ferrocene methanol was dissolved in 125 ml THF and 3.6 g of2-isocyanato ethyl methacrylate were added followed by 1.1 g catalystdibuthyltindilaurate. The solution was stirred for 48 hours and thesolvent was removed. The residue was dissolved in ether and washedthoroughly with deionized water several times. The monomer was furtherpurified by chromatography over silica (ether eluent).

The foregoing description of the invention illustrates and describes thepresent invention. Additionally, the disclosure shows and describes onlythe preferred embodiments of the invention but, as mentioned above, itis to be understood that the invention is capable of use in variousother combinations, modifications, and environments and is capable ofchanges or modifications within the scope of the inventive concept asexpressed herein, commensurate with the above teachings and/or the skillor knowledge of the relevant art. The embodiments described hereinaboveare further intended to explain best modes known of practicing theinvention and to enable others skilled in the art to utilize theinvention in such, or other, embodiments and with the variousmodifications required by the particular applications or uses of theinvention. Accordingly, the description is not intended to limit theinvention to the form disclosed herein. Also, it is intended that theappended claims be construed to include alternative embodiments.

What is claimed is:
 1. A polymer prepared from at least oneorganometallic monomer selected from the group consisting of anorganometallic acrylate, organometallic methacrylate, and organometallicstyrene, wherein the metal is selected from the group consisting ofyttrium, aluminum, iron, titanium, zirconium, and hafnium; and at leastone monomer selected from the group consisting of styrene,alphamethylstyrene, hydroxystyrene, and acetoxystyrene.
 2. The polymerof claim 1 wherein the metal is iron.
 3. The polymer of claim 1 beingfrom at least one monomer selected from the group consisting of2-ferrocenylethyl acrylate, 2-ferrocenylethyl methacrylate,2-(ferrocenylmethyl-2-urethano)-ethyl acrylate and2-(ferrocenyl-methyl-2-urethano) methacrylate, 4-ferrocenylmethylstyrene, and 3 ferrocenylmethyl 4-acetoxystyrene.
 4. The polymerof claim 1 being a copolymer from: a) at least one monomer selected fromthe group consisting of an organometallic acrylate, organometallicmethacrylate, organometallic styrenes, and mixtures thereof wherein themetal is selected from the group consisting of yttrium, aluminum,hafnium and mixtures thereof; and b) at least one monomer selected fromthe group consisting of acrylic acid, methacrylic acid, esters thereofand mixtures thereof; wherein the amount of a) is about 1 to about 90weight % and the amount of b) is about 99 to about 10 weight % basedupon the total weight of a) and b).
 5. The polymer of claim 4 whereinthe monomer b) is selected from the group consisting of 2-hydroxyalkylmethacrylate wherein the alkyl has 1-10 carbon atoms,2-hydroxyalkylacrylate wherein the alkyl has 1 to 10 carbon atoms;acrylic acid, methacrylic acid, alkyl acrylate wherein the alkyl has 1to 10 carbon atoms, aklylmethacrylate wherein the alkyl has 1-10 carbonatoms, chloroalkyl acrylate wherein the alkyl has 1 to 10 carbon atoms,and chloroalkylmethacrylate wherein the alkyl has 1 to 10 carbon atoms.6. The polymer of claim 4 which further comprises at least one monomerselected from the group consisting of styrene, alphamethylstyrene,hydroxystyrene, acetoxystyrene and mixtures thereof.
 7. The polymer ofclaim 1 being a copolymer of alphachloromethyl acrylate and2-ferrocenylethylacrylate.
 8. The polymer of claim 1 being a copolymerof alphachloromethyl acrylate and 2-ferrocenylethylmethacrylate.
 9. Thepolymer of claim 1 being a copolymer of alphachloromethyl acrylate,alphamethyl styrene and 2-ferrocenylethyl acrylate.
 10. The polymer ofclaim 1 being a copolymer of alphachloromethyl acrylate, alphamethylstyrene and 2-ferrocenylethyl methacrylate.
 11. The polymer of claim 1being a copolymer of 2-ferrocenylethyl acrylate, methacrylic acid andt-butyl methacrylate.
 12. The polymer of claim 1 being a copolymer of2-ferrocenylethyl methacrylate, methacrylic acid and t-butylmethacrylate.
 13. The polymer of claim 1 being a copolymer ofalphachloromethyl acrylate and 2-(ferrocenylmethyl-2-urethano-)-ethylacrylate.
 14. The polymer of claim 1 being a copolymer ofalphachloromethyl acrylate and2-(ferrocenylmethyl-2-urethano-)-ethylmethacrylate.
 15. The polymer ofclaim 1 being a polymer of alphachloromethylacrylate, alphamethylstyrene and 2-(ferrocenylmethyl-2-urethano-)-ethyl acrylate.
 16. Thepolymer of claim 1 being a copolymer of - alphachloromethyl acrylate,alphamethyl styrene and 2-(ferrocenylmethyl-2-urethano-)-ethylmethacrylate.
 17. The polymer of claim 1 being a copolymer of2-(ferrocenylmethyl-2-urethano-)-ethyl acrylate, methacrylic acid andt-butyl methacrylate.
 18. The polymer of claim 1 being a copolymer of2-(ferrocenylmethyl-2-urethano-)-ethyl methacrylate, methacrylic acidand t-butyl methacrylate.
 19. The polymer of claim 1 being a copolymerof 2-ferrocenylethyl acrylate, α-methyl 4-acetoxystyrene and t-butylmethacrylate.
 20. The polymer of claim 1 being a copolymer of2-ferrocenylethyl methacrylate, α-methyl 4-acetoxystyrene andt-butylmethacrylate.
 21. The polymer of claim 1 being a copolymer of2-(ferrocenyl methyl-2-urethano-)-ethyl acrylate,α-methyl-4-acetoxystyrene and t-butyl methacrylate.
 22. The polymer ofclaim 1 being a copolymer of 2-(ferrocenylmethyl-2-urethano-)-ethylmethacrylate, α-methyl-4-acetoxystyrene and t-butyl methacrylate. 23.The polymer of claim 1 which comprises at least a two carbon atom chainbetween the metal and acrylate or methacrylate moiety.
 24. The polymerof claim 1 wherein the polymer is further prepared with chloroalkylacrylate, wherein the alkyl has 1 to 10 carbon atoms.
 25. The polymer ofclaim 24 wherein the chloroalkyl acrylate is alphachloromethyl acrylate.26. The polymer of claim 1 wherein the organometallic methacrylate is2-ferrocenylethyl methacrylate.
 27. The polymer prepared from at leastone organometallic monomer selected from the group consisting of anorganometallic acrylate, organometallic methacrylate, and organometallicstyrene, wherein the metal is selected from the group consisting ofyttrium, aluminum, iron, titanium, zirconium, and hafnium; andchloroalkyl acrylate, wherein the alkyl has 1 to 10 carbon atoms. 28.The polymer of claim 27 wherein the chloroalkyl acrylate isalphachloromethyl acrylate.
 29. The polymer of claim 27 wherein thepolymer is further prepared with at least one monomer selected from thegroup consisting of styrene, alphamethylstyrene, hydroxystyrene, andacetoxystyrene.
 30. The polymer of claim 27 wherein the organometallicmethacrylate is 2-ferrocenylethyl methacrylate.
 31. The polymer of claim1 wherein the organometallic monomer accounts for 10% to 70% by weightof the polymer.
 32. The polymer of claim 27 wherein the organometallicmonomer accounts for 10% to 70% by weight of the polymer.